MadSci Network: Chemistry

Re: Decomposing hair

Date: Fri Aug 7 01:12:13 1998
Posted By: John Christie, Faculty, School of Chemistry, La Trobe University, Bundoora, Victoria, Australia
Area of science: Chemistry
ID: 902460314.Ch

For those who are neither medicos nor organic chemistry minors, here is a 
brief run-down of what is going on. Animal hair is largely made of protein, 
and the sort of giant protein molecule that is involved has quite a lot of 
sections of the sulfur-containing amino-acid cystine. The sort of micro-
organisms that live in wet, low oxygen environments like the U-bend traps 
in plumbing, get the energy to keep them alive and multiplying by eating 
their way through any sort of waste organic material. They turn it mainly 
into methane and carbon dioxide. Methane is not much of a problem: it is 
almost odourless, and only relatively small quantities are involved. The 
real problem is that any sulfur that was present in the original organic 
material finishes up as hydrogen sulfide and/or dimethyl sulfide -- rotten 
egg gas -- and these gases are both very toxic and very smelly. A small 
amount goes a very long way!

So you have tried two remedies. It is not surprising that neither will 
work. Antibacterials will kill most or perhaps even all of the current 
colonies of microorganisms. But that will just leave a vacant lot rich in 
nutrients in the microbial world -- it will be rapidly taken over by new 
tenants. Caustic soda works in two ways. It will also kill the current 
colonies of microbiota. And it is an alkali that will react with hydrogen 
sulfide (not dimethyl sulfide!) to form water-soluble and non-smelly sodium 
sulfide. But only for as long as that water stays alkaline. As soon as 
neutral or acidic water gets back into the trap, new colonies of 
mocroorganisms will return, and so will the smell.

The real question that you ask is "any suggestions". As a medico you will 
appreciate that this must be tackled in two parts: prevention amd cure. 

I think I can help with the prevention bit. If there is no convenient 
alternative to your shower for rottweiler bathing, by far the most 
effective thing you can do is to fix a much finer filter over your plug 
hole, so that the hairs are caught in a position where they can 
conveniently be manually removed and disposed of. If no suitable commercial 
product is readily available, I would suggest stretching some nylon or 
fibreglass shadecloth or insect screen over a frame and gluing or screwing 
that over your plughole.

The cure is more difficult. Antibacterials and caustic soda are two of the 
three obvious approaches. I can suggest a third -- an oxidizing agent like 
peroxide, which will permanently convert rotten egg gas to harmless 
sulfates. But none will work very well because of the problems I outlined 
previously. What you need is a "slow release" solution. A slow release 
solution that kills the microbiota does not solve the problem, but merely 
holds it at bay: the existing load of hair will not rot, but just stay 
there for future use. The best solution, though hardest to achieve, would 
be to somehow produce a high oxygen environment in your shower U-bend, so 
as to encourage colonies of aerobic microbes to do the job. They use oxygen 
with the organic matter to produce carbon dioxide; no methane is produced, 
and sulfur is converted to sulfates rather than rotten egg gas. Physically 
removing the current crop of rotting hair from the U-bend may prove easiest 
after all, either by getting in at it, or by devising some way to 
comprehensively push it further down the waste water system.

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